Since crop yield decreases by as much as 30% to 100% in case of cultivating crops without pesticides, it is essential to use the pesticides for improving crop yield. However, improper use of synthetic chemical pesticides in crop production causes several problems such as nonselective toxicity, accumulation of toxic compounds and outbreak of pathogens resistant to the pesticides. One way to handle these problems is to develop biopesticides using antagonistic microorganisms. Biopesticides are roughly classified into plant extracts, microorganisms, natural enemies, natural bioactive substances and genetically modified organisms (GMO). Biopesticides can be safer, more biodegradable, and less expensive to develop than synthetic chemical pesticides.
The study on the development of biopesticides, especially microbial fungicides, has been a major interest in the field of plant pathology, and has been actively carried out for the past 70 years, resulting in more than 40 microbial fungicide products in last ten years.
Meanwhile, Bacillus sp. is a Gram-positive bacterium abundant in soil and is almost as widely researched and commercialized as Pseudomonas Genus. Bacillus sp. produces biologically active secondary metabolites and forms thermostable endospores tolerant to bad conditions. Gustafson Inc. developed a microbial fungicide employing Bacillus subtilis for treating furrows and seeds of cotton and peanut, and it has been sold on the market under a commercial name of Kodiak (Backman et al., Improving Plant Productivity with Rhizosphere Bacteria 3-8, 1994). Further, a microbial fungicide using a mixture of Bacillus subtilis and Bacillus amyloliquefaciens has been introduced into the market in 2001 under a commercial name of BioYield. Numerous Bacillus sp. strains have been used for increasing crop yield in China. In addition, Bayer Inc. developed an agent for controlling soil communicable diseases comprising Bacillus FZB 24, and Taensa Inc. produced a microbial fungicide using the same.
Furthermore, AgraQuest Inc. developed Serenade, a microbial fungicide using Bacillus subtilis QST713. Unlike others using the above-mentioned Bacillus sp. strains, this microbial fungicide is effective against over 40 plant diseases including gray mold, damping-off and powdery mildew. It has been reported that this antagonistic microorganism effectively controls various kinds of plant diseases through several mechanisms such as competition, parasitism, antibiosis and induced resistance, and produces more than 30 kinds of lipopeptides as antibiotic compounds including three groups of iturins, plipastins and surfactins (Ritter, Chemical & Engineering News 81: 30-35, 2003).
In Korea, the study for biologically controlling postharvest root rots of ginseng began in the early 1970, followed by the study for biological control of the red pepper blight, Fusarium wilt of cucumber and strawberry, sesame damping-off and gray mold. However, the study has been unsuccessful due to the instability in the result, difficulty in formulation, poor productivity and so on. The first domestic microbial fungicide using a Bacillus sp. strain is Topseed developed by Greenbiotech Co., Ltd. However, since it has been shown to be effective only against powdery mildew, its application has been quite limited.
The present inventors have endeavored to develop a new microbial fungicide having potent antifungal activity against a wide range of plant diseases, and have found that a plant endophytic bacterium, Bacillus subtilis EB120 isolated from red peppers shows antagonistic activity against several kinds of plant diseases including powdery mildew of barley and cucumber, red pepper anthracnose, rice blast, tomato gray mold, tomato late blight and wheat leaf rust.